Uv liquid steriliser

Abstract

A fluid steriliser comprising a fluid duct having a UV transmissive wall providing a surface area for irradiation, wherein the cross section of the duct is between 1×10 −4 m 2 and 5×10 −2 m 2 and the thickness of the duct defines the depth of fluid flow adjacent the UV transmissive wall of no more than 50mm; a source of UV radiation arranged to irradiate fluid flowing in the duct through the UV transmissive wall such that the UV radiation incident on fluid in the duct has a UV power density; a plurality of mixing stages configured to provide turbulent flow in the fluid and spaced apart along the length of the duct wherein the segments of the duct between the mixing stages are arranged to provide flow adjacent the UV transmissive wall; a flow control means arranged to control the linear speed of fluid flow along the duct based on the length of the duct and the UV power density so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the fluid during the dwell time of the fluid in the duct.

1 . A fluid steriliser comprising:
 a fluid duct having a UV transmissive wall providing a surface area for irradiation, wherein the cross section of the duct is between 1×10 −4  m 2  and 5×10 −2  m 2  and the thickness of the duct defines the depth of fluid flow adjacent the UV transmissive wall of no more than 50 mm;   a source of UV radiation arranged to irradiate fluid flowing in the duct through the UV transmissive wall such that the UV radiation incident on fluid in the duct has a UV power density;   a plurality of mixing stages configured to provide turbulent flow in the fluid and spaced apart along the length of the duct wherein the segments of the duct between the mixing stages are arranged to provide flow adjacent the UV transmissive wall;   a flow control means arranged to control the linear speed of fluid flow along the duct based on the length of the duct and the UV power density so that at least 300 Joules of UV energy per square metre of the surface area for irradiation is provided to the fluid during the dwell time of the fluid in the duct.   
     
     
         2 . The fluid steriliser of  claim 1  in which the mixing stages comprise UV transmissive material wherein the mixing stages are arranged so that UV light from the UV source can reach the interior surfaces of the missing stages when the mixing is filled with UV transmissive fluid. 
     
     
         3 . (canceled) 
     
     
         4 . The fluid steriliser of any preceding claim in which the flow control means is configured such that, in use with fluids having a viscosity of less than 200 centipoise, the pressure drop across the fluid duct is less than 8 bar. 
     
     
         5 . The fluid steriliser of  claim 1  comprising an expansion joint adapted to reduce strain on the UV transmissive wall due to thermal expansion of a wall of the duct, and in which the expansion joint comprises a holder for holding the duct and a resilient adapter coupled between the wall of the duct and the holder and arranged such that the resilient adapter is compressible or extensible to accommodate expansion or contraction of the wall of the duct with respect to the UV transmissive wall. 
     
     
         6 . (canceled) 
     
     
         7 . The fluid steriliser of  claim 5  in which the holder comprises a ring and a collar adapted to be seated about the ring so that the transverse movement of the collar is constrained with respect to the ring. 
     
     
         8 .- 9 . (canceled) 
     
     
         10 . The fluid steriliser of  claim 1  in which the flow control means is configured to control the flow of fluid along the duct such that the average linear speed of the fluid flow between the baffles is between 0.5 and 4 metres per second. 
     
     
         11 . (canceled) 
     
     
         12 . The fluid steriliser of  claim 1  in which the duct comprises a cylindrical outer wall and a cylindrical inner wall comprising the UV transmissive wall, and the outer wall comprises stainless steel. 
     
     
         13 . (canceled) 
     
     
         14 . The fluid steriliser of  claim 12  in which the inner wall of the duct has an internal diameter of at least 36 mm and in which the source of UV radiation comprises a tube lamp having an outer diameter of no more than 34 mm. 
     
     
         15 . (canceled) 
     
     
         16 . A fluid steriliser comprising a duct having a UV transmissive wall and a second wall, wherein the coefficient of thermal expansion of the second wall is different from the coefficient of thermal expansion of the UV transmissive wall and in which the steriliser comprises a movable means configured to be moved to accommodate thermal expansion or contraction of the walls. 
     
     
         17 . The fluid steriliser of  claim 16  in which the movable means comprises an expansion joint in at least one of the second wall and the UV transmissive wall. 
     
     
         18 . The fluid steriliser of  claim 16  in which the expansion joint comprises an extensible member arranged to be extended or compressed along a direction of expansion and a support arranged to provide free play in the direction of expansion and to support the at least one of the second wall and the UV transmissive wall. 
     
     
         19 . The fluid steriliser of  claim 18  in which the support comprises a shoulder and a cover coupled to the shoulder by the extensible member and arranged to cooperate with the shoulder to support the at least one of the second wall and the UV transmissive wall. 
     
     
         20 . A fluid treatment apparatus comprising a plurality of mutually similar units, each unit comprising plurality of elongate tubular ducts and a fluid inlet in fluid communication with a fluid outlet via the plurality of elongate tubular ducts, each duct having:
 a UV transmissive inner wall spaced from an outer wall to enable fluid flow along the tubular duct between the inner wall and outer wall;   a plurality of baffles distributed along the length of the duct and arranged substantially perpendicular to the direction of the fluid flow;   the apparatus further comprising a flow control means configured to control the flow of fluid along the duct such that the average linear speed of the fluid flow between the baffles is between 0.8 and 1.6 meters per second.   
     
     
         21 . The apparatus of  claim 20  in which the flow control means is configured to control the flow of fluid such that the average linear speed of the fluid flow between the baffles is between 1.0 meters per second and 1.4 metres per second. 
     
     
         22 . The apparatus of  claim 20  in which the fluid inlet of each unit of the plurality of mutually similar units is coupled to a common fluid source and the fluid outlet of each unit of the plurality of mutually similar units is coupled to a common fluid sink such that the units are arranged to process fluid in parallel. 
     
     
         23 . The apparatus of  claim 20  in which, in each unit, the plurality of elongate tubular ducts are arranged in series. 
     
     
         24 . (canceled) 
     
     
         25 . The apparatus of  claim 20  in which the interior surface of the inner wall of the duct has a diameter of at least 38.5 mm, preferably at least 39 mm, still more preferably at least 39.5 mm. 
     
     
         26 . The apparatus of  claim 20  in which the interior surface of the outer wall of the duct has a diameter of less than 54 mm, preferably less than 52 mm, still more preferably less than 51 mm. 
     
     
         27 . A method of disinfecting comestible fluid comprising providing fluid into a fluid treatment apparatus comprising an elongate tubular duct having:
 duct inlet, a duct outlet, and a UV transmissive inner wall spaced from an outer wall to enable fruit juice to flow along the tubular duct between the inner wall and outer wall, wherein the cross section of the duct through which fluid can flow has an area of at least 1×10 −4  m 2  and less than 1×10 −3  m 2 ; a plurality of baffles distributed along the length of the duct and arranged at an angle of at least 70° to the direction of the flow;   irradiating the fluid through the UV transmissive wall with UV radiation;   
       controlling the pressure of the juice such that the pressure difference between the duct inlet and the duct outlet is less than 0.4 bar and more than than 0.05 bar. 
     
     
         28 . The method of  claim 27  in which the fluid is one of milk, edible oil, vinegar, beer and fruit juice. 
     
     
         29 .- 40 . (canceled)